1. Field of the Invention
The invention relates to an apparatus for cooling a product, including a condenser structure, an evaporator structure having at least a first evaporator section and a second evaporator section, a refrigerating circuit interconnecting the condenser structure with the evaporator structure, compressor means arranged in the refrigerating circuit between the evaporator structure and the condenser structure for pumping a refrigerant from the evaporator structure to the condenser structure, a heat exchanger structure incorporating the evaporator structure for promoting heat transfer from a product to be cooled to the evaporator structure; the heat exchanger structure including a first heat exchanger section incorporating the first evaporator section and a second heat exchanger section incorporating the second evaporator section, and means for leading the product to be cooled or an intermediate heat transfer medium from the first heat exchanger section to the second heat exchanger section.
2. Background Art
The invention also relates to a method of cooling a product, in which a product is led through a heat exchanger structure, wherein heat is withdrawn from the product by an evaporator structure and transferred from the evaporator structure to a condenser structure into which a refrigerant is compressed, the product or an intermediate heat transfer medium is cooled in at least a first stage and a subsequent second stage, heat being withdrawn from the product or the intermediate heat transfer medium during the first stage by a first evaporator section cooling the product or the intermediate heat transfer medium to an intermediate temperature and heat being withdrawn from the product or the intermediate heat transfer medium during the second stage by a second evaporator section cooling the product or the intermediate heat transfer medium from the intermediate temperature to the desired temperature.
Such an apparatus and such a method are disclosed in U.S. Pat. No. 4,907,417 and are generally referred to as apparatuses and methods for instant cooling of a product. In such apparatuses and methods the product is immediately cooled as it is passed by the heat exchanger. However, the energy consumption of such an apparatus is substantial.
In German patent specification 23 35 899 a method and an apparatus for cooling freshly obtained milk is disclosed, wherein a refrigerating apparatus with a smaller capacity can be used. To achieve this, the milk is first cooled by the refrigerating apparatus to a temperature of 15.degree. C., subsequently transferred into a milk storage tank and finally recirculated from the milk storage tank to the same refrigerating apparatus to be cooled further to the storage temperature of 4.degree. C. A disadvantage of this method is that the product is not immediately cooled to the desired temperature. This is particularly disadvantageous if the freshly milked milk is added to cooled milk already present in the milk storage tank, because the temperature of milk in the tank rises each time fresh, partially cooled milk is added to the tank.